Reference Stress Based Approach to Predict Failure Strength of Pipes With Local Wall Thinning Under Single Loading

Abstract

This paper proposes a new method to estimate failure strength of a pipe with local wall thinning. The method is based on the equivalent stress averaged over the minimum ligament in the locally wall thinned region. The highlight of the proposed method is to propose a simple scheme to estimate the equivalent stress in the minimum ligament. Inspired by the reference stress method for approximate creep stress analysis, approximate estimation equations are proposed for the equivalent stress in the minimum ligament, which are then calibrated using detailed elastic-plastic three-dimensional FE analysis. Remarkably the resulting estimation equations are found to be insensitive not only to pipe and defect geometries but also to material. Comparison of failure loads, predicted according to the proposed method, with published test data for corroded pipes shows excellent agreement, which provides confidence in the use of the proposed method to assess local wall thinning in pipes. Furthermore, the proposed method is conceptually simple and thus easy to be extended to more complex situations.

Structural Integrity Assessment of Major Nuclear Components Using Probabilistic Fracture Mechanics

“…Probabilistic integrity assessment of wall-thinned piping system is conducted with the three evaluation modules. In this case, due to a lacks of field data, the distributions of probabilistic variables are quoted from reference [9] as shown in Table 2 and the limit state function is constructed based on deterministic criteria proposed by Kim et al [10].…”

“…where σ U is ultimate tensile strength and σ local indicated in Eq. 8 is equivalent stress at the deepest point of wall-thinned piping system under internal pressure, global bending and combined loading [11]. Key Engineering Materials Vols.…”

Experimental investigation of the failure behavior of notched wall-thinned pipes

“…A number of experimental and analytical studies have been carried out to understand the failure behavior and to develop a methodology to evaluate the integrity of wall-thinned piping components in an NPP (Deardorff and Bush, 1990;JAERI report, 1993;Miyazaki et al, 1999Miyazaki et al, , 2002Ahn et al, 2002;Kim and Park, 2003;Kim et al, 2004). In these studies, the failure mode, fracture strength, and fatigue strength of wall-thinned pipes were investigated under various loading conditions and defect geometries.…”

Ultimate creep load and safety assessment of P91 steel pipe with local wall thinning at high temperature

“…At room temperature the researches on pipe with LWT focused on the stress analysis [3][4][5][6][7], limit load [8][9][10][11][12][13][14], fracture behavior [15][16][17][18][19][20], safety assessment [21] and fatigue behavior [22,23]. Different pipe types (straight pipe [9,10], elbow pipe [8,11,12] and tee pipe [20]), different load types (internal pressure [4,8], bending load [10,17] and combined loads [7,13,14]) and different defect numbers (single LWT [3][4][5]9,10] and multiple LWTs [21]) were considered by different research methods (finite element method [3,7,12] and experimental method [8,9,17]). Many meaningful results have been obtained.…”